<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 这里index是一个固定的接口名，你要是把index的名字改了就不可以了 -->
    <form action="http://127.0.0.1:3009/" method="post">
        <!-- 正常提交一定要写name属性 -->
        <input type="text" name="username">
        <input type="password" name="password">
        <input type="submit" value="提交">
    </form>
</body>
</html>